1. Technical Field
The subject matter described here generally relates to fluid reaction surfaces with specific blade structures that are formed with a main spar, and, more particularly to wind turbine blade stowage arrangements.
2. Related Art
A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy. If that mechanical energy is used directly by machinery, such as to pump water or to grind wheat, then the wind turbine may be referred to as a windmill. Similarly, if the mechanical energy is further transformed into electrical energy, then the turbine may be referred to as a wind generator or wind power plant.
Wind turbines use one or more airfoils in the form of a “blade” to generate lift and capture momentum from moving air that is them imparted to a rotor. Each blade is typically secured at its “root” end, and then “spans” radially “outboard” to a free, “tip” end. The front, or “leading edge,” of the blade connects the forward-most points of the blade that first contact the air. The rear, or “trailing edge,” of the blade is where airflow that has been separated by the leading edge rejoins after passing over the suction and pressure surfaces of the blade. A “chord line” connects the leading and trailing edges of the blade in the direction of the typical airflow across the blade. The length of the chord line is simply the “chord.”
Wind turbines are typically categorized according to the vertical or horizontal axis about which the blades rotate. One so-called horizontal-axis wind generator is schematically illustrated in FIG. 1 and available from GE Energy of Atlanta, Ga. USA. This particular configuration for a wind turbine 2 includes a tower 4 supporting a drive train 6 with a rotor 8 that is covered by a protective enclosure referred to as a “nacelle.” The blades 10 are arranged at one end of the rotor 8, outside the nacelle, for driving a gearbox 12 connected to an electrical generator 14 at the other end of the drive train 6 arranged inside the nacelle along with a control system 16. An anemometer 18 and/or other sensing devices may be mounted on or near the nacelle of the wind turbine 2.
The wind turbine blades 10 may be telescopic or retractable. For example, U.S. Pat. No. 6,902,370 discloses a telescoping wind turbine blade having a moveable section that is nested within a larger fixed section. FIG. 5 of that patent illustrates a slider track that is attached to the fixed blade portion and a slider that is attached to the moveable portion. U.S. Pat. No. 6,726,439 also discloses retractable rotor blades for power generating wind an ocean current turbines. However, even these wind turbine blades and/or their component parts are often so large that they are difficult to store and/or transport.
Various techniques have been proposed to address the difficulties associated with wind turbine blade stowage. For example, U.S. Pat. No. 6,983,844 discloses a package system for transporting wind turbine blades where the root section of a blade is packed in a first package while the tip is packed in a second package with inner packing material made of glass fibre, wood, or foamed rubber. European Patent Application No. 1,659,026 discloses a transport device for an elongate object such as a rotor blade for a wind turbine or the like. U.S. Patent Publication No. 2005/0180833 discloses a transport container for wind turbine blades and U.S. Patent Publication No. 2006/0251517 discloses a method of transporting and storing a wind turbine blade and